[PATCH v2] mtd/maps: gpio-addr-flash: new driver for GPIO assisted flash addressing
Mike Frysinger
vapier at gentoo.org
Wed Jun 3 08:51:49 EDT 2009
This driver lets people use GPIO's for additional address lines in case
their processor does not have enough address lines already.
Signed-off-by: Mike Frysinger <vapier at gentoo.org>
Signed-off-by: Bryan Wu <cooloney at kernel.org>
---
v2
- add kernel doc suggested by Ben
- touchup style pointed out by Ben
- avoid duplication of gpio array pointed out by Ben
- optimize code a bit
drivers/mtd/maps/Kconfig | 10 ++
drivers/mtd/maps/Makefile | 1 +
drivers/mtd/maps/gpio-addr-flash.c | 311 ++++++++++++++++++++++++++++++++++++
3 files changed, 322 insertions(+), 0 deletions(-)
create mode 100644 drivers/mtd/maps/gpio-addr-flash.c
diff --git a/drivers/mtd/maps/Kconfig b/drivers/mtd/maps/Kconfig
index 82923bd..05f6c08 100644
--- a/drivers/mtd/maps/Kconfig
+++ b/drivers/mtd/maps/Kconfig
@@ -500,6 +500,16 @@ config MTD_BFIN_ASYNC
If compiled as a module, it will be called bfin-async-flash.
+config MTD_GPIO_ADDR
+ tristate "GPIO-assisted Flash Chip Support"
+ depends on MTD_COMPLEX_MAPPINGS
+ select MTD_PARTITIONS
+ help
+ Map driver which allows flashes to be partially physically addressed
+ and assisted by GPIOs.
+
+ If compiled as a module, it will be called gpio-addr-flash.
+
config MTD_UCLINUX
tristate "Generic uClinux RAM/ROM filesystem support"
depends on MTD_PARTITIONS && MTD_RAM && !MMU
diff --git a/drivers/mtd/maps/Makefile b/drivers/mtd/maps/Makefile
index 2dbc1be..d9cbd8a 100644
--- a/drivers/mtd/maps/Makefile
+++ b/drivers/mtd/maps/Makefile
@@ -62,3 +62,4 @@ obj-$(CONFIG_MTD_INTEL_VR_NOR) += intel_vr_nor.o
obj-$(CONFIG_MTD_BFIN_ASYNC) += bfin-async-flash.o
obj-$(CONFIG_MTD_RBTX4939) += rbtx4939-flash.o
obj-$(CONFIG_MTD_VMU) += vmu-flash.o
+obj-$(CONFIG_MTD_GPIO_ADDR) += gpio-addr-flash.o
diff --git a/drivers/mtd/maps/gpio-addr-flash.c b/drivers/mtd/maps/gpio-addr-flash.c
new file mode 100644
index 0000000..6724255
--- /dev/null
+++ b/drivers/mtd/maps/gpio-addr-flash.c
@@ -0,0 +1,311 @@
+/*
+ * drivers/mtd/maps/gpio-addr-flash.c
+ *
+ * Handle the case where a flash device is mostly addressed using physical
+ * line and supplemented by GPIOs. This way you can hook up say a 8meg flash
+ * to a 2meg memory range and use the GPIOs to select a particular range.
+ *
+ * Copyright 2000 Nicolas Pitre <nico at cam.org>
+ * Copyright 2005-2009 Analog Devices Inc.
+ *
+ * Enter bugs at http://blackfin.uclinux.org/
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/map.h>
+#include <linux/mtd/partitions.h>
+#include <linux/mtd/physmap.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#include <asm/gpio.h>
+#include <asm/io.h>
+
+#define pr_devinit(fmt, args...) ({ static const __devinitconst char __fmt[] = fmt; printk(__fmt, ## args); })
+
+#define DRIVER_NAME "gpio-addr-flash"
+#define PFX DRIVER_NAME ": "
+
+/**
+ * struct async_state - keep GPIO flash state
+ * @mtd: MTD state for this mapping
+ * @map: MTD map state for this flash
+ * @gpio_count: number of GPIOs used to address
+ * @gpio_addrs: array of GPIOs to twiddle
+ * @gpio_values: cached GPIO values
+ * @win_size: dedicated memory size (if no GPIOs)
+ */
+struct async_state {
+ struct mtd_info *mtd;
+ struct map_info map;
+ size_t gpio_count;
+ unsigned *gpio_addrs;
+ int *gpio_values;
+ unsigned long win_size;
+};
+#define gf_map_info_to_state(mi) ((struct async_state *)(mi)->map_priv_1)
+
+/**
+ * gf_set_gpios() - set GPIO address lines to access specified flash offset
+ * @state: GPIO flash state
+ * @ofs: desired offset to access
+ *
+ * Rather than call the GPIO framework every time, cache the last-programmed
+ * value. This speeds up sequential accesses (which are by far the most common
+ * type). We rely on the GPIO framework to treat non-zero value as high so
+ * that we don't have to normalize the bits.
+ */
+static void gf_set_gpios(struct async_state *state, unsigned long ofs)
+{
+ size_t i = 0;
+ int value;
+ ofs /= state->win_size;
+ do {
+ value = ofs & (1 << i);
+ if (state->gpio_values[i] != value) {
+ gpio_set_value(state->gpio_addrs[i], value);
+ state->gpio_values[i] = value;
+ }
+ } while (++i < state->gpio_count);
+}
+
+/**
+ * gf_read() - read a word at the specified offset
+ * @map: MTD map state
+ * @ofs: desired offset to read
+ */
+static map_word gf_read(struct map_info *map, unsigned long ofs)
+{
+ struct async_state *state = gf_map_info_to_state(map);
+ u16 word;
+ map_word test;
+
+ gf_set_gpios(state, ofs);
+
+ word = readw(map->virt + (ofs % state->win_size));
+ test.x[0] = word;
+ return test;
+}
+
+/**
+ * gf_copy_from() - copy a chunk of data from the flash
+ * @map: MTD map state
+ * @to: memory to copy to
+ * @from: flash offset to copy from
+ * @len: how much to copy
+ *
+ * We rely on the MTD layer to chunk up copies such that a single request here
+ * will not cross a window size. This allows us to only wiggle the GPIOs once
+ * before falling back to a normal memcpy. Reading the higher layer code shows
+ * that this is indeed the case, but add a BUG_ON() to future proof.
+ */
+static void gf_copy_from(struct map_info *map, void *to, unsigned long from, ssize_t len)
+{
+ struct async_state *state = gf_map_info_to_state(map);
+
+ gf_set_gpios(state, from);
+
+ /* BUG if operation crosses the win_size */
+ BUG_ON(!((from + len) % state->win_size <= (from + len)));
+
+ /* operation does not cross the win_size, so one shot it */
+ memcpy_fromio(to, map->virt + (from % state->win_size), len);
+}
+
+/**
+ * gf_write() - write a word at the specified offset
+ * @map: MTD map state
+ * @ofs: desired offset to write
+ */
+static void gf_write(struct map_info *map, map_word d1, unsigned long ofs)
+{
+ struct async_state *state = gf_map_info_to_state(map);
+ u16 d;
+
+ gf_set_gpios(state, ofs);
+
+ d = d1.x[0];
+ writew(d, map->virt + (ofs % state->win_size));
+}
+
+/**
+ * gf_copy_to() - copy a chunk of data to the flash
+ * @map: MTD map state
+ * @to: flash offset to copy to
+ * @from: memory to copy from
+ * @len: how much to copy
+ *
+ * See gf_copy_from() caveat.
+ */
+static void gf_copy_to(struct map_info *map, unsigned long to, const void *from, ssize_t len)
+{
+ struct async_state *state = gf_map_info_to_state(map);
+
+ gf_set_gpios(state, to);
+
+ /* BUG if operation crosses the win_size */
+ BUG_ON(!((to + len) % state->win_size <= (to + len)));
+
+ /* operation does not cross the win_size, so one shot it */
+ memcpy_toio(map->virt + (to % state->win_size), from, len);
+}
+
+#ifdef CONFIG_MTD_PARTITIONS
+static const char *part_probe_types[] = { "cmdlinepart", "RedBoot", NULL };
+#endif
+
+/**
+ * gpio_flash_probe() - setup a mapping for a GPIO assisted flash
+ * @pdev: platform device
+ *
+ * The platform resource layout expected looks something like:
+ * struct mtd_partition partitions[] = { ... };
+ * struct physmap_flash_data flash_data = { ... };
+ * unsigned flash_gpios[] = { GPIO_XX, GPIO_XX, ... };
+ * struct resource flash_resource[] = {
+ * {
+ * .name = "cfi_probe",
+ * .start = 0x20000000,
+ * .end = 0x201fffff,
+ * .flags = IORESOURCE_MEM,
+ * }, {
+ * .start = (unsigned long)flash_gpios,
+ * .end = ARRAY_SIZE(flash_gpios),
+ * .flags = IORESOURCE_IRQ,
+ * }
+ * };
+ * struct platform_device flash_device = {
+ * .name = "gpio-addr-flash",
+ * .dev = { .platform_data = &flash_data, },
+ * .num_resources = ARRAY_SIZE(flash_resource),
+ * .resource = flash_resource,
+ * ...
+ * };
+ */
+static int __devinit gpio_flash_probe(struct platform_device *pdev)
+{
+ int ret;
+ size_t i, arr_size;
+ struct physmap_flash_data *pdata;
+ struct resource *memory;
+ struct resource *gpios;
+ struct async_state *state;
+
+ pdata = pdev->dev.platform_data;
+ memory = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ gpios = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+
+ if (!memory || !gpios || !gpios->end)
+ return -EINVAL;
+
+ arr_size = sizeof(int) * gpios->end;
+ state = kzalloc(sizeof(*state) + arr_size, GFP_KERNEL);
+ if (!state)
+ return -ENOMEM;
+
+ state->gpio_count = gpios->end;
+ state->gpio_addrs = (void *)gpios->start;
+ state->gpio_values = (void *)(state + 1);
+ state->win_size = memory->end - memory->start + 1;
+ memset(state->gpio_values, 0xff, arr_size);
+
+ state->map.name = DRIVER_NAME;
+ state->map.read = gf_read;
+ state->map.copy_from = gf_copy_from;
+ state->map.write = gf_write;
+ state->map.copy_to = gf_copy_to;
+ state->map.bankwidth = pdata->width;
+ state->map.size = state->win_size * (1 << state->gpio_count);
+ state->map.virt = (void __iomem *)memory->start;
+ state->map.phys = NO_XIP;
+ state->map.map_priv_1 = (unsigned long)state;
+
+ platform_set_drvdata(pdev, state);
+
+ i = 0;
+ do {
+ if (gpio_request(state->gpio_addrs[i], DRIVER_NAME)) {
+ pr_devinit(KERN_ERR PFX "failed to request gpio %d\n",
+ state->gpio_addrs[i]);
+ while (i--)
+ gpio_free(state->gpio_addrs[i]);
+ kfree(state);
+ return -EBUSY;
+ }
+ gpio_direction_output(state->gpio_addrs[i], 0);
+ } while (++i < state->gpio_count);
+
+ pr_devinit(KERN_NOTICE PFX "probing %d-bit flash bus\n",
+ state->map.bankwidth * 8);
+ state->mtd = do_map_probe(memory->name, &state->map);
+ if (!state->mtd) {
+ for (i = 0; i < state->gpio_count; ++i)
+ gpio_free(state->gpio_addrs[i]);
+ kfree(state);
+ return -ENXIO;
+ }
+
+#ifdef CONFIG_MTD_PARTITIONS
+ ret = parse_mtd_partitions(state->mtd, part_probe_types, &pdata->parts, 0);
+ if (ret > 0) {
+ pr_devinit(KERN_NOTICE PFX "Using commandline partition definition\n");
+ add_mtd_partitions(state->mtd, pdata->parts, ret);
+ kfree(pdata->parts);
+
+ } else if (pdata->nr_parts) {
+ pr_devinit(KERN_NOTICE PFX "Using board partition definition\n");
+ add_mtd_partitions(state->mtd, pdata->parts, pdata->nr_parts);
+
+ } else
+#endif
+ {
+ pr_devinit(KERN_NOTICE PFX "no partition info available, registering whole flash at once\n");
+ add_mtd_device(state->mtd);
+ }
+
+ return 0;
+}
+
+static int __devexit gpio_flash_remove(struct platform_device *pdev)
+{
+ struct async_state *state = platform_get_drvdata(pdev);
+ size_t i = 0;
+ do {
+ gpio_free(state->gpio_addrs[i]);
+ } while (++i < state->gpio_count);
+#ifdef CONFIG_MTD_PARTITIONS
+ del_mtd_partitions(state->mtd);
+#endif
+ map_destroy(state->mtd);
+ kfree(state);
+ return 0;
+}
+
+static struct platform_driver gpio_flash_driver = {
+ .probe = gpio_flash_probe,
+ .remove = __devexit_p(gpio_flash_remove),
+ .driver = {
+ .name = DRIVER_NAME,
+ },
+};
+
+static int __init gpio_flash_init(void)
+{
+ return platform_driver_register(&gpio_flash_driver);
+}
+module_init(gpio_flash_init);
+
+static void __exit gpio_flash_exit(void)
+{
+ platform_driver_unregister(&gpio_flash_driver);
+}
+module_exit(gpio_flash_exit);
+
+MODULE_AUTHOR("Mike Frysinger <vapier at gentoo.org>");
+MODULE_DESCRIPTION("MTD map driver for flashes addressed physically and with gpios");
+MODULE_LICENSE("GPL");
--
1.6.3.1
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